Description of Project (as per applicant abstract): The proposed effort will lead to novel prototype devices which will greatly improve the lives of those who are hearing impaired. One of the primary complaints of hearing aid wearers is that they have significant difficulty sorting out speech in noisy environments. In an attempt to address this, the hearing aid research community has examined directional array technology which would tend to attenuate the sounds arriving from behind the hearing aid users. While these devices can provide a significant improvement in speech intelligibility, they often require the user to wear a number of microphones connected through wires, which is cosmetically unacceptable or the microphones must be incorporated into the frames of eyeglasses. A much more desirable and practical approach is to incorporate an array (possibly composed of only two microphones) within the structure of an existing in-the-ear or in- the-canal hearing aid. Such a device could provide an enhanced rejection of sounds from the rear beyond that provided by the pinna. The present study uses a novel, highly innovative approach to develop a directional hearing aid microphone which relies entirely on a unique, passive mechanical structure to achieve its directionality. The approach provides significant advantages over previous attempts to solve this problem by 1) reducing the reliance on electronic signal processing and, as a result, has the potential of significantly increasing battery life by reducing power consumption and 2) utilizing the technology of silicon micromachining which facilitates the integration of mechanical sensing and processing devices along with electronic circuits in a very small package. The problem of developing small directional receivers has been addressed extensively in nature. By applying the principles used in natural, biological systems, it will be possible to develop practical directional hearing aids. In the proposed study, recently discovered mechanisms that are used by insects for sound source localization will be utilized in order to develop prototype directional microphones suitable for use in hearing aids. Industrial collaboration will provide technical assistance and will ensure that the resulting device satisfies manufacturability and packaging constraints. In order to facilitate the development of a production-ready device, a prototype fabrication run will be developed at Sandia National Laboratories which will then be passed on to the industrial collaborators.